1. Field of the Invention
An electrical cable includes a light-transmitting cable sheath in which are embedded a plurality of insulated conductors at least two of which are helically twisted, the cable being provided with visible markings that indicate where one can electrically engage a selected one of the twisted conductors by an insulation-piercing contact, together with a method for manufacturing such a cable.
2. Description of Related Art
Electrical cables, especially flat-strip cables that have parallel and/or mutually twisted-together conductors (the latter by way of the so-called “twisted-pair technology”) are known as such. The following are furthermore cited with regard to the state of the art: German patent No. DE 38 90 470 C2, and the U.S. Pat. Nos. 6,270,598, 5,606,151 and 6,476,329.
A special problem connected with these cables occurs during the contacting of the conductors that are twisted together with each other by means of insulation-penetrating contacts, which must contact the mutually twisted-together conductors at precise spots that are suitable for this purpose. These can, for example, be places where the conductors lie next to each other in the cable plane or orthogonally relative to the cable plane above each other. The parallel sides likewise are not always positioned in a defined manner with respect to each other so that they are not always securely retained.
To solve this problem, it has been proposed in the U.S. Pat. No. 6,476,329 to eliminate the twisting of the conductors over a predetermined longitudinal extent and that one can contact the conductors in this area by means of insulation-penetrating contacts. But that makes the production of the cable more expensive. Besides, the elimination of the twisting over a predetermined area does not have an advantageous effect on signal transmission with the cable. It is therefore desirable to create a cable with continuously twisted conductors.
In the Yamamoto U.S. Pat. No. 6,412,265, an insulation-penetrating cable is disclosed wherein the cable sheath contains perforations. But these perforations are regularly distributed over the cable sheath and are not so fashioned that they can be used as markings or that they will represent such markings because they do not permit the alignment of the insulation-penetrating contacts in such a manner that the twisted conductors will be contacted at the appropriate places. This applies all the more since the twisting into the longitudinal cable direction is not quite constant so that the markings are not to be arranged entirely in a precise grid, but rather preferably are placed exactly where the optimum point for contacting the conductors is or was determined in each case.
The present invention was developed to correct this problem and to develop the typical cable in such away that it will be possible to provide for the secure contacting of conductors and especially also—if present—of the twisted conductors with insulation-penetrating contacts, in particular, insulation-piercing contacts. Furthermore, a process is to be provided for the production of the cable as well as a connecting device for the purpose of contacting the invention-based cable.